The spinal column of bones is highly complex anatomical structure that includes over 20 bones coupled to one another, housing and protecting critical elements of the nervous system having innumerable peripheral nerves and circulatory bodies in close proximity. Despite its complexity, the spine is a highly flexible structure, capable of a high degree of curvature and twist in nearly every direction. The more than 20 discrete bones of an adult human spinal column are anatomically categorized as one of four classifications—cervical, thoracic, lumbar, or sacral—and are coupled together sequentially to one another by a tri-joint complex that consists of an anterior disc and two posterior facet joints. The anterior discs of adjacent bones are cushioned by cartilage spacers referred to as intervertebral discs or vertebrae. The cervical portion of the spine comprises the top of the spine up to the base of the skull and includes the first seven vertebrae. The intermediate 12 bones are thoracic vertebrae, and connect to the lower spine comprising the 5 lumbar vertebrae. The base of the spine comprises sacral bones, including the coccyx. With its complex nature, however, there is also an increased likelihood that surgery may be needed to correct one or more spinal pathologies.
Genetic or developmental irregularities, trauma, chronic stress, tumors, and disease can result in spinal pathologies that either limit this range of motion or threaten critical elements of the nervous system housed within the spinal column. A variety of systems have been disclosed in the art which achieve this immobilization by implanting artificial assemblies in or on the spinal column. Such systems require surgical implantation during a spinal surgery.
During implantation of such systems, retractors and distractors are commonly used. After an incision is made in a patient's skin, a surgeon will normally use a retractor to retract the patient's skin to create a surgical opening. Then, a distractor is normally used to distract two adjacent vertebral bodies to enlarge the disk space so that the surgeon can insert a spinal implant cage. Typically, the retractor and the distractor are two separate instruments, which results in additional instruments that must be purchased prior to surgery, handled during surgery, and cleaned or discarded after surgery.
Therefore, it is desirable, during surgical implantation of spinal devices, to have an integrated retractor-distractor for use with modular bone screws that allows for percutaneous delivery, independent alignment between bone screws, and improved reliability, durability, and ease of installment of said devices.